Note to ALL PROSPECTIVE STUDENTS: I am currently
looking for a student to work on a NASA-funded project using both remote sensing
and isotopic techniques to examine dust production and Ca cycling in semi-arid
environments. If you are interested, please contact me. See my "Calcium research page" for more information.
**VIEW IMAGES OF MY FIELD WORK IN THE BLACK ROCK DESERT (NV)**
The general objective of my work is to understand the global cycling of elements
such as Fe and Ca at the surface of the Earth. More specifically, I am interested
in processes such as weathering, fluvial transport, and marine sedimentation.
The research questions of interest to me involve how the following processes affect
not only the mass fluxes of Fe and Ca, but also the isotopic composition of each
in the natural environment:
- Physical and chemical weathering of igneous, sedimentary, and metamorphic rocks (including the formation of dust);
- Soil development, including organic complexation and redox reactions;
- Fluvial transport and estuarine interactions;
- Surface ocean processes (such as biological uptake of Fe), dissolution of
dust, precipitation of secondary minerals, and cycling between the surface
and deep ocean;
- Deep ocean processes, such as particulate sinking and subsequent sedimentation and diagenesis.
I am particularly interested in combining geochemical data (either elemental or isotopic) with numerical models. That is the approach I have taken so far in my research. I have used these techniques to investigate the fidelity of geochemical proxies, such as Sr and Ca, in marine carbonates. Combining modeling and geochemical measurements in marine carbonate sediments, I have been able to say something about:
- Chemical evolution of the ocean over the last 35 Myr,
- Recrystallization rates over both million-year and 10 kyr time scales,
- Diagenetic changes in carbonates over time (with regard to elemental concentrations of Sr, as well as Sr and Ca isotopes),
- The equilibrium fractionation factor between CaCO3 and dissolved Ca2+ in the marine sedimentary column, and
- Mechanisms controlling Ca isotope fractionation during calcite precipitation.
Such observations have direct implications for paleoclimate studies that use proxies such as Mg/Ca and Sr/Ca ratios to say something about sea surface temperatures. However, such techniques may also be applied to oxygen isotope studies, which have ice volume, as well as paleotemperature, implications.
In the near future, I am interested in applying the techniques I have developed in isotope mass spectrometry as well as numerical modeling and remote sensing to examine general questions such as:
- How elements cycle at the surface of the Earth,
- How we can use this information in models to constrain the chemical evolution of the ocean as well as the degree of weathering at the Earth's surface,
- How diagenesis affects geochemical proxies over million-year time scales, and
- How we might confidently use geochemical proxies to tell us something about the past.
I am interested in examining those isotope systems I have already mentioned, in addition to other novel intermediate mass isotope systems and more conventional systems (such as B). I am interested not only in using isotopes and associated analytical techniques but also in electron microscopy, laser ablation, and remote hyperspectral methods to achieve my research goals.
Please see the Fe research page or the Ca research page for more detail on my research interests.